Trema, aliens have advantage in s1, humans have advantage in s2, and s3 would be balanced if they didnt get to it twice as fast as aliens, if aliens dont have tyrants humans dont need luci.
Norf seems to understand best why im throwing all these ideas out here, humans have a huge assortment of weapons for all different situations, mg to kill dretches, shotguns for quick damage, lasgun for continuous fire, saw for buildings and anything getting close, mass driver to deliver damage accurately at range with no delay, pulse rifle for big damage and surpression, flamer for burning anything that gets close, chaingun for bringing down big aliens, luci for spam and sometimes killing things in 1 or two shots, they also get grenades to multi-kill and hurt buildings and scare aliens off, battery packs for ammo, jetpacks to fly, 2 types of armor, a helmet for radar, and I am still probably forgetting something.
Aliens get 5 classes including grangers, 9 if you count "advanced" classes as seperate, again including grangers, humans have more options than that just counting weapons.
Aliens attacks are also all basicly the same and involve running right up to the humans while being shot at with all those different weapons, not that that isnt usualy effective but sometimes it isnt enough.
Range really is a huge advantage alot of the time(like when camping), sure you can dodge a human and run in close but what happens when the guy next to him has a flamer? you are out of options.